Electrostatic scanning mechanism for scanning both tips and rings of calling lines and combining the results of these scanning operations



Aprll 13, 1954 NEWBY 2,675,427

ELECTROSTATIC SCANNING MECHANISM FOR SCANNING BOTH TIPS AND RINGS 0F CALLING LINES AND COMBINING THE RESULTS OF THESE SCANNING OPERATIONS Filed DEC. 21, 1951 v 2 Sheets-Sheet l DELA Y DEV/CE WR/77/VG HEAD LAY DEV/CE A TTO/PNE V April 13, 1954 NEWBY 2,675,427

ELECTROSTATIC SCANNING MECHANISM FOR SCANNING BOTH TIPS AND RINGS 0F CALLING LINES AND COMBINING THE RESULTS OF THESE SCANNING OPERATIONS Filed Dec. 21, 1951 2 Sheets-Sheet 2 2 3 I 1 49/45 T T bl l l l +8 MA By N. D. NEWBV A TTOR VE V Patented Apr. 13, 1954 UNITED STATES PATENT OFFICE Neal D. Newby, Leonia, N. J., assignor to Bell Telephone Laboratories, Incorporated, New 'York, N. Y., a corporation of New York Application December 21, 1951, Serial No. 262,842

25 Claims.

This invention relates to improvements in electrostatic scanning and distributing mechanisms, circuits and methods and more particularly relates to an improvement in the electrostatic scanning arrangement of the type disclosed in my copending application Serial No. 185,929, filed September 21, 1950.

In the scanning arrangement disclosed in said copending application provision was made for scanning or sampling the potential condition of one side of a plurality of lines or calling circuits at repeated intervals. Such an arrangement has certain shortcomings in case of trouble conditions which it is incapable of recognizing. For example, if the grounded side of the line is employed for scanning purposes then an accidental ground on the other side of the line renders the line inoperative but no indication is received at the central office to indicate that any trouble exists upon the line. Likewise, should the battery side of the line be scanned then no indication is given should leaks or faults or opens in the other side of the line be encountered.

In accordance with the present invention certain of these difiiculties are overcome by means for scanning the potential condition of both sides of a calling or subscriber's line, a trunk circuit, or other calling or signaling lin or circuit and then combining the scanned output of both sides of the line. Under these circumstances a greater output is obtained and at the same time it is much easier to recognize trouble conditions on the line and give an alarm or other indication at the central ofiice to the maintenance forces so that the trouble condition may be removed at the earliest possible moment and with the least amount of effort and with the shortest interruption of service.

While it is possible to provide two scanning devices such as disclosed in the above-identified copending application such devices are complicated and expensive and where two are provided it will be necessary to maintain the two scanning mechanisms in synchronism so that the outputs may be combined or otherwise compared and utilized for signaling purposes.

In accordance with the present invention the above-described difficulties are largely eliminated by applicants present scanning mechanism in which each side of the line is scanned, one after the other in rapid succession by the same scanning apparatus and then theoutputs from these two scanning operations combined to give'any desired output indication.

In accordance with one specific exemplary 1 embodiment of the present invention the scanning or distributor devices have two adjacent segments connected to opposite sides of called lines and the two line segments are separated from corresponding pairs of segments of other lines by a shielding segment. The output from the scanning arm which sweeps adjacent the various segments is combined so that the resulting signal is a function of the voltage of each of the line conductors of the respective lines.

The improved arrangement in accordance with this invention has a further advantage that a large voltage difference usually exists between various line segments so that a better output wave form is obtained at all times from the scanning or distributing mechanisms.

In accordance with one specific embodiment of the present invention the magnitude of a pulse of one polarity, obtained as a result of scanning one side or conductor of a calling line or trunk, is added to the magnitude of a succeeding pulse of the opposite polarity obtained as a result of scanning the other side or conductor of the same calling line or trunk and an output pulse is obtained having a magnitude which is a function of the sum of the magnitudes of said pulses of opposite polarity.

Another feature of this invention relates to circuits, apparatus and methods of distinguishing between the sum of pulses of different magnitudes.

Another feature of this invention relates to circuits, apparatus and methods for obtaining a signaling condition which is a function of the sum of the signaling conditions on both line conductors of a signaling, transmission, or communication line.

Another feature of this invention relates to circuits, apparatus and methods of restoring the summing circuit to a predetermined condition between the scanning of each pair of segments assigned to the various calling lines.

Another feature of this invention relates to circuits, apparatus and methods for obtaining a signaling condition which is a, function of the rate of change of the electrical condition of a scanning member as it passes between two adjacent segments which segments are usually connected to the respective line conductors of a signaling line.

Another feature of this invention relates to circuits, apparatus and methods for obtaining an output signaling condition of one character when the rate of change of the electrical condition of the scanning member exceeds a predetermined value and obtaining a different output of the electrical condition when the rate of change of the electrical condition of said scanning member does not exceed'said predetermined value.

Another feature of this invention relates to circuits, apparatus and methods for scanning the respective conductors of signaling lines and deriving a predetermined electrical conditiomresponsive to the closed condition of. said line, andifor deriving a different electrical condition1responsive to an open condition of said line.

In the exemplary embodiments of this invention described herein in detail, provision is made to scan, test, or sample the voltage conditioniofw.

both sides or both conductors of a telephone subscribers line. It is to be understood,-=however, that the signaling conditions of each-of the line conductors of any type of a calling or signaling valineucircuit may .be. similarly tested, scanned, or ,sampled andthat both line conductors of the trunk .ortoll linecircuit may likewise be scanned .Hor-sampled-inla similarmanner in accordance with the present invention.

4 Briefly, in accordance with an exemplary embodiment of the present. invention, a distributor nor scanning mechanismis provided for a pluralitylof calling signaling, subscriber or trunk lines .or .pluralities of groups of said lines. The distributor or; scanning mechanism is provided with a segment for each .conductor of each of the trunk lines, subscribersnlinesor signaling circuits and each pairoflsegments .isseparated and shielded from an. adjacent pair of segments which are ,lassignedtoand interconnected with another line by means of a shielding segment which is usually connectedto some. fixed or reference voltage or ;-potential source. whichmay include ground potential. Any suitable type of filter or filtering elements may be interconnected between the line conductors and the respective segments including interconnecting .resistors, distributed capacity of the wiringsconductors and also the capacity of t he segments'as-rwell as anydesired added cappacity or other. impedance and filter elements and networks.

A scanning arm is provided and rotatably sup- -:-,-l orted so that it may be rotated past each of the line segments. .Inaccordance with the present invention-a scanning member .passes adjacent to the line segments but does not engage or come gin. contactwith them. The scanning element or wmember is. shielded and the scanning member to- ,-gether-v with the shield: which shield is alsorotated ..with, thezscanning memberare conected. to an gamplitying device which repeats the voltage applied to the scanning member to the shielding amember .and alsoto control circuits.

:Inoneembodiment of this invention control circuits comprisenacircuit for adding a magni- .,.t-ude.;cf the =yoltage conditions induced in the scanning memberas it passes adjacent the two -vsegments oftany given signaling path or line and 1 then'causes an output pulse to be generated which ;.pulse has aafixed. magnitude when the sum of the two scanned pulses exceeds a predetermined :reference magnitude.

.In accordance with another embodiment of this invention the control circuits comprise a differentiating circuit for differentiating the voltage condition of the scanning conductor and other control, apparatus for generating an output pulse or voltage of predetermined character whenthe rate. of change of the voltage of the scanning conductor' exceeds a" predetermined "magnitude, In

.. naling line.

"properly synchronizing the switching apparatus accordance with this embodiment of the invention switching circuits are provided for restoring the differentiating circuit to its initial condition and preventing the operation of the output circuits except when the scanningiconductor passes between two segments interconnected with a sig- Control means are also provided for -.so' that the;differentiating means is rendered effectiveatzthei desired time. Fhe output pulses are employed in combination with suitable controlmeans for recording the electrical condition of theline.

. In'theexemplary embodiments set forth herein -in.-de.tail theabove-described scanning arrangements are arranged to cooperate with a magnetic storing or recording equipment such as described ,in: ,my above-identified copending application.

w of this invention may be more readily understood from the following description of an exemplary embodiment thereof when'read with reference to the attached drawing in which:

Fig. 1 shows the details of'an exemplary em- 1 bodimentof the invention in which a scanning and recording mechanism is employed for receiving and storing calling signals. In the arrangement shown in Fig. l the voltage induced on the scanning member when it passes one of the segments connected to a line is added to the voltage induced in the scanning member when it passes I the other segment connected to the same line.

Fig. 1A shows details of'the control circuit of H another-exemplary embodiment of this invention .the exemplary. scanning arrangement in accordance with. the. present invention is designed to cooperate with a magnetic recording and storing mechanism.

. suitable for. use in combination with a magnetic .'.,Fig. 1-. shows an exemplaryembodiment of an electrostatic, scanner and related circuits in accordance with the, present invention which are drum for recording and storing calling signals such as dial signals employed in automatic telephone switching systemsand other types .of signalsemployed in other types of calling arrangements.

..,As shown inEig. 1 in the exemplary embodiment setforth herein invdetail a scanning member is mounted on the same shaft as the magnetic recording and. storing drum so that it rotates at the same velocityv and at thesame relative positionwith respect to said magneticdrum. .However, when desired, this scanning mechanism may be driven from someother shaft which may be geared to. the magnetic drum driving means or otherwise synchronized with the drum or drum driving mechanisms.

The'scanningdevice as shown in the upper left-handportion of Fig. 1' comprises a rotating conductive arm 25 insulatedlymounted on shaft I00 which is, the same shaft employed to rotate the drum I04. The end 21 of the rotating arm 25 passes adjacent to but does not touch or make contact with a plurality of segments 32a, 32b, 33a, 331), etc. This arm in approaching each of the fixed segments forms a condenser with the respective fixed segments and has a voltage or current induced on or in the arm 25 in accordance with the voltage or potential of the individual segments to which this arm passes adjacent. The rotating arm 25 is surrounded by a shielding member 26 which rotateswith but is insulatedly supported from the arm 25. The rotating element 26 is likewise insulatedly supported from the shaft I00. A pair of stationary rings 23 and 24 is provided and insulatedly supported around shaft I00. The ring 23 is electrostatically coupled to the rotating member 250i the scanning or distributor mechanism and the stationary ring 24 is capacitatively coupled to the shielding member'26. While these rings 23 and 24 are shown in the drawing as being placed around and in close proximity to the respective rotating elements of the distributor orscanning mechanism with which they cooperate to form an electric circuit, it is to be understood that any suitable form of electrostatic capacitative coupling may be employed or that any other suitable type of coupling may include brushes resting on slip rings. However, the capacitative coupling is employed in the present embodiment of this invention because it is particularly well adapted for coupling to the rotating elements which in turn are capacitatively coupled to the segments 32a, 3212, 33m 331), etc., because this form of coupling introduces substantially no extraneous'signals, noise currents or other interfering or stray currents which currentswould interfere With the low level signals picked up by the rotating member 25 aswill be described hereinafter.

The segments as shown in the drawing of the scanning or distributor mechanism are arranged in two groups, one group comprising pairs of se ments assigned and connected to the various lines which are to be scanned or tested in succession and the other group comprising agroup of shielding members or segments which'segments separate each of the pairs of segments assigned to a given line. One segment of a pair is connected to the tip conductor of the transmission line and the other segment is connected to the ring conductor, the terms tip and ring conductors merely specifying or defining the different line conductors.

In an exemplary embodiment of this invention the recorder comprises a magnetic drum, the magnetic surface of which provides sufiicient area, to be used in common by about a thousand subscribers lines, each line having an arc of approximately .36 degree. A scanning electrode 25 is mounted on the shaft of the drum and its associated amplifiers 2| and 20 are employed to amplify the received signals sufliciently to actuate other devices and switching circuits.

Any suitable arrangement of the line electrodes and the scanning element may be provided. For example, the line electrodes may be arranged on a fiat plate perpendicular tothe rotating shaft and the scanning electrode arranged to be rotated adjacent these line electrodes. The line electrodes may be arranged on the inner surface of a ring as shown in the drawing and the scanning or distributing element arranged to rotate adjacent the inner surface of this ring and thus adjacent the line electrodes. As the scanning electrode 25 passes each of the line electrodes such as 32a, 32?), etc., the electrical condition of the line may be recorded in the space on the magnetic drum reserved for it as will be explained hereinafter. The sampling rate, that is, the speed of rotation of the scanning electrode must be sufliciently high to recognize each of the significant characteristics of the pulses or other received signals which are to be recorded. Assuming that the signals to be received are in the form of dial pulses, then the speed of rotation of the magnetic drum and also the scanning electrode 25 must be such that this electrode makes at least one complete revolution during each open interval of the dial and at least another complete revolution during each closed interval of the dial. When desired, the scanning electrode may make more than one revolution during each of these intervals and the system will operate in substantially the same manner as described hereinafter.

Inasmuch as the scanning electrode rotates at a relatively high speed and inasmuch as the line segments such as 32a, 32b, 33a, 3310, etc. are of relatively small dimensions measured in degrees of arc, the scanning circuit with its amplifier and other related equipment must be designed to respond to pulses of relatively short duration and, therefore, must be arranged and designed to respond to high frequency currents. If the calling or sub-scribers line is subject to these high frequency currents, it will be desirable and sometimes necessary to provide suitable filtering elements between the line circuit and the electrostatic scanner. The filtering elements may be in addition to and they may include the capacity of the various segments and associated wiring and circuits as well as the resistance of the wires, circuits, etc., and also added resistance, capacity and inductance elements.

As shown in the drawing, each of the line segments for each calling line is connected to a resistor through which the line current of that line flows. Consequently, the voltage applied to the line segments of the scanning mechanism is the battery voltage either plus or minus the voltage drop across the line resistor connected thereto. When the line i open, i. e. idle, no line current will flow. Consequently, there will be no voltage drop across the line resistors with the result that substantially the entire battery voltage is applied to the electrodes of the given line. When line current flows as Will be described hereinafter, the voltage drop across the respective resistors causes the voltage or potential applied to the scanning electrodes to be less than the battery voltage. In other words, when the line is idle the voltage difference between the two adjacent segments connected to a given line will be the maximum. When the line is closed line current flows over the line and through the resistors connected between battery and each of the line conductors so the voltage of each line conductor and thus of the distributor segment connected thereto tend to approach the voltage of the other as more and more line current flows and will be substantially equal to each other for short lines having little or no line resistance.

In the exemplary embodiment of this invention shown in the drawing, positive and negative batteries or sources of voltage are connected to the respective line conductors. However, the polarities of these batteries or sources may be reversed, or a single source of either polarity may be conneotd to either of the rlineiliccnductors :asand g-ro-u nd connected to the other conductor the soanhing-" arrangementawill' operate. equallyowell w hen suitable change zareimade in various bias voltages':and.theodiodes polediin the proper 'direetion and' the line condu'ctor: scanned in" the rproper'ordcr.

ummth element, a'ofiilthe represent according -mechanism comprises atmagnetic storage device. Inthe-exemplary:embodiment. ofzxthistinizention *s'et forth herein the: magneticsmaterialzemployed iers recording :andi-storing: signals comprises a i layer'lupon a' rotating drum. However, any suitably moWing: layer or surface of magneticzmaterial such aidiscpbelt; fetc -which; moves'zina closed or:reentrant path-may beemployedequally -well in ccmbination' withrthe .circuitszand other apparatus embodying this invention.

"rcThe"drumremployed inza'the exemplarwembodiment 'r's'et forth: 'lrcreiniiin-detail'rmay be econ- 'structed ."of suitable: structural materialras; for

example, brass; bronzextubing; stainless steel tub ing; aluminumztubing; orsany other suitable xtype of structural: mateiial including plastic materials andother insulating. materials; the purpose of the 'structural rmaterial beingxatozi provide: a. cylindriw'c'al surface which may be rotated about its axis by cdrivingmeans'ofnuitabletype such as an-electric e motor. Theizdrum may be driven directly by or fibyrm'eansrzof:gearswbelts oriany other 'form of emechanical?'connectiomtand the motor senergized a suitable source. of'power, including bat stories orjriother' means. The' speed of the motor iSiZHOlL' critical; ands'zneedr not bemaintained in --synchronism with any other apparatus, so long as itrotates the shaft 15R] and thus the drum Hi4 and: the: .icapacitativei :collector 'or 1 distrib utor or .1scanning;element-{ 25 at-dthe samespeed and in .rsynchronismiwith'each other and'sulliciently ast to "provideatonewsampling 'interval for; each line v during each of the shortest-(signalingconditions on the line which it is desired to recognize.

The surface of the drum is accurately true running and is provided with a layer of magnetic material which an exemplary embodiment employing metallic drums may take the form of-an A plurality of recording and'pick-up coils comprising one or more windings on a ferromagnetic core structure are mounted'in close proximity to the plated surface but not in contact with it. It

vvill be convenient hereafter to speak ofthec re- The signals-tube cording process as writing. written'or recorded are of a pulse-like character and have one or theother of two different Values Or characteristics, one being called Xsignals and the other 0. signals. The recordlngcoils #60,

and the pick-up coils comprise a core structure having pole tips brought close together and placed in close proximit to the magnetic surface of'the drum. Coils are wound on each of these cores and when employed fer recording or Writing; 65 wheel having a plurality of substantially uniform the coil is employed to producev a magnetic flux across the pole tips which alters the magnetic condition of the surface of the drum. In-the pick-up coils the magnetic condition of the drum induces a flux change between the pole-pieces;

/ with the magnetic condition of the drum.

The circumferential area of the drum which- 5 8 cipasseszrrlmmediatelyrbeneatlmther pole-tips Ibf a lza-givemcoilcordieaohis :definedsas a.-;=channe1wnd :t-iahat parttofzthechannelcwhich is:directly .:under "or" immediately-1adjacent 13011110162 tips "of: aizgiven 5 ;.=coil'wi'1en-a:.rpulse:'cf recording or writingzcurrhent axis applieditoothe'rcoil.is 'lmownsas at: cell orrzelei onentaloarea 21.0fl the :channel' "and" assigned r :to a -lgicemline. In-pthercase of a multiplicityg'of; recording coilsrorswritinge headsra-nd: a multiplicity lo ofnpickeup'coils; or. reading. heads,: the a regate :1.otthe:ielementalaareasx or: cells which-are under otherseveralz;coils:atiany one instant ofttimez is -'.d8fiIlEd as: art-slot? and: isaassigned. to: a; given dine. 'Elbe: grouppofncells or elemental areas-las- Sl3116d-1't0 a'icalling. line passunder: the'respec-tive coils at; substantially the" instant of .time thatthe scanning electrode? is passingover .the-segvment: of the, electrostatic distributor assigned to othe same line. ;The simplest arrangement'of such 11a slot'is a rectangular area'running'parallelwith ..the--axis on=the surface of :the'drum. lt-is to'be innderstood, however, that in the. usual case-this :islot will be-rmoremf acomplicatedform-and is znotrtherefore limited to such a'rectangulararea. 2:5 'When the variouspick-up coils or-recording cells /01. heads. are stagg ered or arranged-in. thez-lform .ofahelix aroundthe drum the slot-maybehelical; or may havea saw-toothdormwor other discontinuous shape depending uponthe location of 3c the various recording andrpickeup =coils.

A-recording amplifier is providedsfor eachvrez' 'cording coil and is provided-with-two vinput leads ..-designated X and O. .These amplifierslare nor- -mally'biased so that substantially-no current ows.,-in-the recording .coil windings. When. it is. desired to recordsan .X- signal a high= -positive voltage with-respect tcground is applied-to the X r-input :lead v and when it -iS5dGSiIGd to -record [an 0 signal a high positive voltage with respect to 4 ground is applied to the 0 input lead.

A pick-up or reading amplifier is also provided for each-pick-up coil. 'I -he'pich-up orreading amplifiers have two. output leads. or terminals, one designated X and the other 0. i In the exem- -.lplary embodiment of this invention described in detail herein when Osignals pass underthe polepieces of therpick-up coil connectedlto the respective amplifiers, a low positive voltageis applied to sthe X output leads orterminals and. a highposi- CO ftive voltage is applied to the O output-terminals. When an 2; signal passes under-the pole tips of a. ,..pick.-up coil, a. high positive voltage is applied to .the Xoutput terminal. of=the pick-up ampli-fier individual to said coil and a low-positive voltage is applied to the 0 output terminal bythe respective pick-up amplifier.

.In addition to the pick-up and recording. coils located adjacent the magnetic drum described abovaadditional pick-up coils such-as and 5| ,are provided for generating timing I and syn- .l. chronizing pulses. As-shown in the" drawing uthese coils are located adj acent the periphery of the timing wheel llll which is shown to be in the form of a gear wheel. Coil 5D is adjacent the spaced'teeth or poles while coil 5| is adjacent the "timing wheelrlflrhaving. a single gear toothv or :gpole. Eachof the-teeth or poles of the Wheel adjacent coil 50 generates a pulse which is employed to controlthe recording of signals in the drum as "will be'described hereinafter. Duringeach revo- Jslution a'single pulse is generated in coil 5| which isused to resto-renumerous circuits to their initial condition so these circuits may'start from a given 75. initial condition once ..during. each revolution.

Consequently, errors in the circuits will not be additive for more than one revolution of the drum. While special coils so and are shown adjacent the gear or tooth wheels for generating timing purposes, it is also within the scope of this invention to provide the timing pulses from pickup coils such as to and 5! located adjacent channels on the magnetic drum which channels will have the synchronizing pulses recorded in them in any suitable manner such as by an oscillator or continuous pulse generator or the like. However, in the exemplary embodiment set forth herein the timing pulses are generated by means of the tooth wheels which are mounted upon the same shaft or at least driven at the same speed as the magnetic drum and usually from the same motor or other driving means. The output of coils 50 and 5| is amplified by the respective amplifiers Bil and BI. Output coil 50 and amplifier 60 are so designed that a high positive outputpulse'is obtained for each tooth of the gear wheel which passes under the pole-pieces of coil 50. The amplifier Gil contains the necessary pulse forming, pulse shaping means and means for otherwise controlling pulse characteristics as required. In an exemplary embodiment of this invention, the pulse output from amplifier 60 for each of the teeth of the gear wheel under coil 50 has a duration of approximately one-tenth the time required for a cell of the magnetic surface of the drum as defined above to pass under a pick-up coil. This pulse duration is not critical and satisfactory results may beobtained with pulses of such a duration.

The output from amplifier 61 comprises a pulse of high negative voltage or polarity for each revolution of the drum or revolution of the single tooth wheel. This pulse has a duration which is appreciably greater than the duration of the timing pulses obtained from amplifier to'but still shorter than the time required for a cell to pass under a recording or pick-up head.

The signals to be recorded. will comprise either one or the other of the two different signaling conditions such as voltage or potentialconditions across the line resistor, depending upon whether the line is opened or closed as will be described. One of these signaling conditions is called an X signal herein and the other of these signaling conditions is called an 0 signal. These two different signaling conditions, i. e., X signals and 0 signals are represented by different currents or voltages or different voltage conditions or different current conditions in different circuits, conductors and terminals in the system. These X signals may also be represented by different magnetic conditions in parts of the equipment. These signaling conditions most frequently comprise a voltage or current of one polarity, i. e.,

positive or negative, 'of relatively high, large, or

maximum magnitude and a voltage or current of the same polarity but of relatively low or minimum magnitude. When desirable these signaling conditions may be represented by other voltages or currents such as by positive and negative currents or voltages of the same or difierent magnitudes, or by current and no current, i. e., a current of substantially zero magnitude, or by a voltage and no voltage, etc.

The operation of the system may be better undertsood and the initial operation of the system improved. if it is assumed that the drum is ini tially magnetized by applying a substantially continuous current to each of the recording coils of the main recording drum or section and substantially saturating the magnetic material in the drum a it passes between the pole-pieces of each of the recording coils in one of the magnetic conditions caused by one of the two diiferent types of signals or voltage conditions to be recorded in the drum. Thus it is assumed that this voltage will be in the same direction as produced by the so-called 0 signal when it is desired to record such a signal in the drum. of course, the opposite or X signal will then comprise magnetizing the drum in the reverse direction between the pole-pieces. In some instances, it is desirable to provide a third type of magnetization which will produce no voltage in the pick-up or read-- ing coil. Such a magnetic condition is readily obtained by orienting an additional coil adjacent to the same channel and rotating the pole-pieces with respect to the channel so that they are degrees displaced from the pole-pieces of the recording coil and the corresponding pick-up coil. This additional coil is continuously supplied with a recording current or employs a permanent magnet to provide a continuous recording field between its'pole-pieces. Thus an 0 is recorded in the magnetic material by orienting the so-called magnetic vectors in one direction, which direction causes a voltage of one polarity to be ob tained from the pick-up coil or coils when this portion of the drum passes under the pole tips. The recording of an X signal will apply a reverse magnetization to the magnetic material and thus in effect will orient the magnetic vectors in a direction substantially degrees from the first direction and thus cause a voltage of the opposite polarity in the pick-up coil. The erasing or third magnetic condition will cause the magnetic vectors to be rotated at an angle of 90 degrees to the first direction and thus cause no voltage to be induced in the output of the pick-up coil.

When only two magnetic conditions are required then the first or zero condition in general does not cause a voltage to be inducted in the pick-up coil, whereas the opposite magnetic condition representing an X signal causes a voltage of a predetermined polarity and wave shape to be inducted in the corresponding pick-up coil. It should be noted that the pick-up coils, recording coils and all of the control equipment therefore together with the electrostatic distributor or scanning mechanisms in accordance with this invention are common to all of the lines assigned to the slots on a given magnetic drum. The various elemental areas on this drum called cells, however, are individually assigned to different ones of these lines and at all times during the call accurately record the electrical condition and the history of the electrical condition of that line. The cells or slots or elemental areas assigned to a given line are employed for recording the condition of only that line and are never employed to record the condition of any of the other lines individual to the drum.

Considering now the operation of the system and referring more particularly to Fig. 1, two lines E4 and I5 are shown in detail.

Each of these lines is provided with a calling switch such as ill and H, respectively, and dials i2 and it or other suitable signaling devices. These lines may be of different lengths from short lines to long lines which may extend over considerable distances as in the case of telephone subscribers lines, annunciator lines, etc. Each line is connected to sources of electrical energy through resistor elements as shown in the drawing. For example, in the exemplary embodiment denser 420 will become sufliciently charged so that the left-hand section of tube 419 will start to conduct and cause the current flowing through the right-hand section to be interrupted and the circuits of the single-cycle multivibrator restored to their normal and stable condition. The time constants of condenser 420 and its related charging and discharging circuits are so selected that this circuit returns to its normal condition as described above.

Each "of the timing pulses which controls the recording of signals is also applied to a delay device 425 which delays these pulses for a sufficient interval of time so that ample time is provided to permit recording and storing as described hereinafter.

At the end of such an interval of time a delayed pulse from the delay device 425 is applied through coupling condenser 426 to the control grid of tube M3. This pulse causes current to flow through tube 453 and discharges the right-hand terminal of condenser 410 so that at the termination of the pulse from the delay line 425, condenser HO will be again in condition to respond to the voltages from amplifier 20 in response to the scanning element 25 passing adjacent the next succeeding pair of line segments which segments will be connected to another calling or subscribers line. In discharging condenser 42!) as described above, a positive pulse may be applied to the control grid of the left-hand section of tube 419 which positive pulse may aid in restoring the circuits of this tube to their normal condition as described above.

Thus, so long as the lines remain open a negative pulse is repeated through the diode M to the left-hand grid of tube H9 which in turn causes the current flowing through the left-hand section of tube M9 to be interrupted and current to flow through the right-hand section of this tube. As a result, insuilicient voltage is applied to the lead 421 to the recording equipment to cause any recording or storing at this time.

Assume now that the subscriber closes switch I!) which completes a circuit over his line so current flows from the positive battery connected to resistor 15 and over the line conductors of line M to negative battery connected to resistor !8. This current causes voltage drops across resistors 16 and I8 which voltage drops reduce the magnitude of. the voltage applied to the two segments 32a and 3212-. Consequently, voltage pulses of reduced magnitude are repeated by amplifier 28 as the scanning arm 25 passes adjacent the segments 32a and 32b. The reduction in magnitude of these voltages is sufiicient so that the sum of the magnitudes of the, two voltages is less than the voltage of the biasing source 4H5. Conseouently. no voltage is repeated through the diode M5 at this time. As a result, the left-hand section of tube M9 remains conducting and the right-hand section remains nonconducting. At this time the shunting negative pulse is not applied to the coupling condenser 42! with the result that substantially the entire volt age of battery 422 is applied to the input lead 42! of the magnetic recording equipment which equipment responds and causes a signal to be recorded. as will be described hereinafter.

Should either side of the line become inadvertently grounded the voltage applied to the corresponding segment 32a or 3212 will be reduced to such a value that this voltage together with the voltage from the opposite side of the line when added together by the summing circuit in 14 the manner described above is insufflcient to overcome the biasing voltage 4|6 with the result that the line will appear to have a permanent signal or trouble condition applied to it which condition may be recognized by suitable circuits at the central ofiice.

In the embodiment of this invention as shown in Fig. 1A, Fig. 1A is substituted for the portion of Fig. 1 below and to the left of line 460, the circuits and apparatus are arranged to respond to the change in voltage condition on each scanning conductor. Referring to Fig. 1A, for example, the output of the scanning amplifier 20 is applied through the coupling condenser M0 to a difierentiating and switching circuit comprising tube 45!! and diodes 45I, 452 and 454 as well as resistors 453 and 456. Tube 450 is employed as a switching tube and is normally biased so that this tube is non-conducting. As a result, a suificiently high positive voltage is connected to the diodes dill and 452 in the forward direction so that these diodes have a very low resistance or impedance and thus maintain a substantial shunt or short-circuit upon the conductor 458. Likewise, the biasing battery 453 is poled in such a direction as to bias the diode 454 in the back or reverse direction so that its impedance is high and permits substantially no current to flow from conductor s53 through the coupling condenser ill. As the scanning electrode 21 passes from one segment to the adjacent segment, the two segments connected respectively to the two conductors of a line, a positive pulse is applied to the control element or grid of tube 450 which causes this tube to become conductive. This pulse is applied through the shaping circuit 451 from the output of the timing amplifier 69). The shaping circuit 451 may include suitable delay or phasing equipment to properly time the pulse so that it is applied at the time indicated. The pulse may be of'any suitable length and may start when the sensing conductor is adjacent the first of a pair of segments connected to a line and end when the sensing conductor arrives adjacent to the second segment. The length of this pulse may be varied so as to include most of the time when the scanning conductor is adjacent both of these segments or it may be shortened so that it includes only the time the scanning conductor is between the two segments connected to a given signaling line.

The application of a positive pulse to the grid of tube 450 at this time causes current to flow in the output or anode-cathode circuit of this tube. Inasmuch as the cathode is connected to a negative voltage the anode voltage is reduced to a lower voltage than is ever developed upon conductor 458 due to the operation of the signaling circuits as will be described hereinafter. As a consequence, the bias on the diodes '45! and 452 is reversed so that these diodes become nonconducting and of a high resistance, thus removing the circuit or shunt from the conductor 458. At this time the voltage applied from the ampli fier 20 will be changed from a relatively high positive voltage'to a relatively low positive voltage or to a high or low negative voltage or, in other words, changed in a negative direction or manner. This voltage change is applied to the coupling condenser M0 which causes a voltage drop across resistor 453. The voltage drop across resistor 453 at this time is substantially proportional to the rate of change of the output voltage from amplifier 20 as applied through the condenser 410. Condenser 4H1 is made sufficiently smallraseisizreiston 453%550- thatzthertimerconstant: of this combination iszrelativelynshorti-: In otherw wordsatheocurrentu fiowingrgthrough :resistor 453 at :this time is ccontrolled "byothe condenser *4 I rat thanbythe'magnitudeofrthe resiston653. s

As pointed out hereinbefore.,-:if theiiine is open, substantially full linelrbattety-is applied to the segments? connectedntothe open line withthe result: that the tvcltagemn'z these signals: will'be a 'maximu irvalues Consequently, since ':thescanning: conductortravels: at a :suostantiallya' uniform speedccr velocity the"rate of change" of voltage of istherscanningz conductor as it passes flGilliOlliE- segment connected-to a given" open line to zthe'rother' segment :connected to the open line-1 wilivbes 'a maximum;

Lil: wisegiftherline is. closed the voltage *ap plied-tcvthetwosegments: is rreduced due to a" voltage iron as described herein with the result thattthewoltage of thestwose'gments connected;

tweencthese segments-becomes much less and inthe "case' of a short line: approaches zero.- As a result when" the 'scann'ing element passes from one; segment to th'e-f-adiacentsegment which is connected to" the conductors "of" an closed line" much lessvoltage changa is induced on the-scan ningrcond-uctor' and since this conductor travels at a-"- su stantially uniform' angular" speed or velocity "as "pointed out above the rate of change of'voltagc of'the scanning-element is much less;

Thevoltage appliedwacross resistor-453 at'this timedue to thechange in voltage onthe-scanning element aspbtained from the scanning amplifie! 2!! is i connected through dio'de l5 to the output. 'couplihgcondenser fl Fl==whichcondenser is in turn connectedto theleft hand grid- OfthQ tuhe If the rates-of change-of wvoltage on the scanningelement is a maximmn the'voltagedrop across resistor 453 will be a'maximum with the result that this voltage "will be of sufficient magnitude to overcome: the bias "battery voltage 55-and r thus "reversexthe "bias on" the diode 454 with the result that this diode will become-con 4 ducting and present-a low-impedanceto the volt seedevelcped across resistor 453-:at'this tlme'and can this voltage to --be applied through-"the ccupling'con'denser' 4 IT- to the "left 'hand' control grid-of'tubeilflr" a On the other handyif "the line isclo'sed as thescanning conductor 2I moves from one'of *the segmentsconnected' to the closed: line to the other connected tothis closed line the voltage developed across resistor -453-will be less 5 their the oiased' voltage from *battery' 455 with theresult'that the bias on the diode "454 does not reverse. Conscquentlyythis"lower voltage is not transmitted to-the condenser 4!? but is instead attenuatecl by the "high impedance" of thediode 45%; As-a result," a negative'voltage orpulse is transmitted. through'ccndenser M1 to the control grid ofthe left-hand section of tube "M9 'inre' spcnse -to anopenline whereas "no such voltage vered-to this'grid iii-response to a closed 65 I Tube M9 operates at this'time as'described -n in the same manner as described with reference to Fig. 1. Consequently, a positive pulseor. signaling. condition is applied to the outputconductor. 42.! when the line isclosed and a low orhegative voltage is applied to conductor 427, whenuthe line is open.

After. the termination of the. pulse. applied. to. the..,c0nt1ol; grid/of .tubeu450," tube fill-ceases to conduct with. theresult the-ta high positive volt- 16: age iswgain wapplleda .to .itheslozwwstexminalmofit diode I which-voltage.- again zpassesndiodes 45h and-. 552 to.--,-the-rconducting idirection andseffecm tively discharges .the. s conductors 458 land the right--l1and terminahozhcondenser 14 M anda-thus. restoresethe diifcrentiatfing-circuitato wits-initial, condition and maintains iti-in thiscondition mntilw another; positive pulserdssappliedsto!the. control" grid of :tube 450 as .the scanning"conductortthen..

passes from one segmentito-theiotheriwhich;seg-h mentsware-connected :to lineaconductors oi. anothelw line.- At; -..this= itime the vI.abovedescribed operation will" be: repeiakteda. This operation is. repeated-v for aeachi ot;-.-thea dinessinrotation-v and, wheathe scanning-conductorsagain returns tot the first line, the operation describednhoveds; again repeated: This operation; is thus repeated for 1 each "revolution": of the, drum ;\or scanning element.

Thusgso longas thcalineszremains operative and-l idle 'th'e '-volta-ge :ofi-:lead- 421- is maintained.isul'lw.- ficiently low at the'recordingomsampling periods which are (controlled-by theroutput .ofiamplifiet. ;:so that no signalsare recorded in-.-the.-mannen.

1 described hereinaftere Howeven; when :the/subm scribes desires towmahea calLtheline-Hcircuit.isi closed and linewurrentfiows over thesline-andfiasv a result: a sufiicientlyt-positive-ivoltage is applied. to the lead. 42-! tozcause awsignalsto rberecorded. or stored. in the magnetic equipment-inane. manner setiiorth heneinafter.:. Thus each time. the distributor arm orescanmngwelementW25 passes segments. 32a .andw 2E whenuthe line. ,I 44s. open the voltage of lead.fllriswreducedstosuclt a value that the .gateacircuits -GI.,.- 20 In andFGZ,

2 I I eithendo notrrespond zto-thissvoltageior else these circuits causesfl signalsqto the recordedati these times. However, eachrtimesthe scanning. element 25.passes-segmentsv3lasand-32bwhen. line- Imis closed the voltages .om leadJZL are. not reduced so that the- .poaitiva -vo1tage .from bat-.1 tery l22sisv applied:to gatercircuits @201 and I L. The gates-circuits. respond..-tor.this.-high .positive, voltage and cause X signalsitoiberrecorded..as.-will be! described hereinater.-.

The operation of the.- system in response @toPsig-i nals: ifromcother lines such aslines. I 5 and other. lines, trunks, and. circuits not shown, -is substane. tia-lly the same asrdescrihed .-above:with reference 7 to line .I 4 each: otsthe dine .conductorsof these other. lines beingascanned in. SUOCGSSiQIL-cfllld the outputiromthe scanning ofrthetwoline conduc-l tors "of .each. line- :or .circuincombined. and. em-.. ployedto contnoltherecording and storingequip mentm The- -signalsrrecordedlin. the... magnetic. equip-- ment .are called-.X signals whenlinecurrentflows ovenline ..I 4. -..After..the line hasonce. rbeenuclosedt on a .call andv then ,openediche -magnetlaequip; ment. is arranged-to. :record this open conditions The recording. of the open condition. underthese circumstances iscalledan .0 signal.

For convenience inzrefe'rring. to these direc: tions of magnetization the left-hand coil of head III, for example, as shownin the drawing is assumed toproduce a directionpf. magnetization in elemental. areas ot-rthe drum .called an X signal while the..right-hand coil is assumed to produce a directioncf magnetization in the .ele-. mental areas of the surface of the drumcalled anO signal It is to be understoodhowever, that the coils that. produce the X. signal and thecoils. that produce the 0 signal may. be .wound. .upon both of the poleT-pieces oftherecordinghead .I I I.'. As shown. in .theldrawinathi; coilslof the .record;

ing head. III are connected to the output circuit of a recording or writing amplifier IIIl. As shown the amplifier III) is provided with two input leads, one designated X and the other 0. Both of these leads are normally maintained at a relatively low Voltage near ground potential by the gate circuit 20!. These input leads connect to terminals 2 and 3 of amplifier H which are coupled through condensers to the grids of the respective tubes 3 and 3I2 as shown in Fig. 2. In the exemplary embodiment the input grids of the amplifier tubes 3H and 3I2 are normally maintained or biased at a negative voltage with respect to ground and as a result no output current flows in the output circuit of amplifier Ilfi so that under these conditions the magnetic conditions of the surface elements of the drum passing under the pole tips of coil I I I are not changed.

Gate circuits such as GI comprise a plurality of rectifiers or diodes which may be of the germanium crystal type, or other suitable forms of crystals or combinations of crystals or high vacuum diodes. The gate circuits have an input aircuit shown at the bottom of the rectangle such as 2M which is connected to the output of the synchronizing amplifier 60. The gate circuit has inputcircuitsshoWn at the left-hand side of the rectangle or box I which in turn are connected to the rectifiers 206 and 208. This gate circuit also has an input lead shown at the right-hand side ofthe rectangle in turn connected to the rectifier element 201. Each of the input leads to the gate circuits have either one or the other of two different voltage or current conditions applied to it. In the exemplary system described herein in detail the gate circuits are arranged to have their input circuits or terminals connected to relatively low impedance circuits which will apply either a high positive voltage of say about '75 volts or more to the input terminal or a low positive voltage of say about volts or less thereto.

So long as a low positive voltage is applied to any one or more of the inputs current fiows from battery 200, and from any of the other inputs having a high positive voltage applied to it, through the diode connected to the relatively loW positive voltage with the result that the common point which comprises an output from the gate circuit is maintained at or near the voltage of the relatively low voltage applied to that input lead or leads. When the voltage applied to all of the input terminals on the left-hand side is a high positive voltage, the gate circuit is arranged so that it will apply a high positive voltage to the X input lead to amplifier I I0 in response to a high positive synchronizing pulse supplied from the synchronizing amplifier 60 to the common point between the diodes 204 and 205, with the result that this change in voltage causes an X signal to be recorded in the corresponding cell or unit area. in the surface. of the drum passing under the recording coil III at this time. Likewise when a high positive voltage is applied to the input lead connected to the diode 201, a high positive voltage is repeated to the 0 input lead to amplifier IIO when a high positive synchronizing pulse is applied from the synchronizing amplifier 60 to. the common point between the diodes 2M and 205 with the result that an 0 is recorded in the magnetic element of the drum passing under the recording head II I at this time.

The gate circuits such as GI shown within therectangle 2M may be arranged in a plurality of different manners. These gate circuits may be arranged so that a high positive voltage applied,

to any one or the input leads will cause a high positive voltage to be repeated to the corresponding output lead in response to the application of a synchronizing pulse from the synchronizing lead. Such gate circuits are sometimes called or gate circuits, that is, circuits. in which outputs appear in response to a high positive voltage applied to any one or more of the input leads. Alternatively, the gate circuits may be arranged such that a high positive voltage has to be applied to all of the input leads or all of a group of the input leads before a high positive voltage is repeated to the corresponding output lead. Such circuits are frequently called and circuits. Such circuits are obtained by applying suitable potentials to the diode elements and properly orienting the diode element. These circuits may also be arranged so that combinations of the two types of circuits may be employed when desired. Furthermore, the voltages applied to these circuits may be such that input voltages so applied to. the input leads prevent a high positive output pulse instead of permitting one, as described above.

For example, with respect to the gate circuit GI, it is necessary for a high positive voltage to be applied to the right-hand terminal of the diode 201 to cause an 0 signal to be recorded by the recording coil I II in response to a high positive synchronizing pulse from the synchronizing amplifier 60.

With respect to the inputs required to cause the recording coil to record an X signal in the corresponding cell of the magnetic drum, the voltage of both of the input leads on the left-hand side of the gate GI must be a high positive voltage. However, in the absence of a recorded X signal passing under the pick-up coil I I5 at this time the output from the X lead from amplifier i it; is a low positive voltage and the output from the 0 lead of amplifier H6 is a high positive as will be described hereinafter with the result that a high positive voltage is applied to the diode 2%. Consequently, when the voltage of lead 421 becomes more positive in response to the scanning electrode 25 passing over segments connected to a closed line a high positive potential is applied to the left-hand terminal of the diode 208 and as a result when the synchronizing pulse from the amplifier lid is applied to the gate GI, the voltage of the X signal input lead to amplifier l Iii becomes a high positive voltage and causes an X signal to be recorded in the corresponding cell under the recording head i I I at this time. No high positive voltage is applied to the 0 input lead to amplifier H0 at this time. Then the arm 25 will move on to the next pair of segments or terminals of the distributor or scanner. In case the next line is also busy or has current flowing over it, an X signal will be written or recorded in the next cell. Conversely, if the next line has no current flowing in it at this time, an X signal Will not be written or recorded in the succeeding cell because the lead 427 will not be sufficiently positive and thus will not cause the application of a high positive voltage to the lefthand terminal of diode 268.

After the above-described X signal is written in the cell asigned to line I4, in the manner described above, this cell will pass around the drum and pass under the pick-up coil or reading head H2 and cause an output voltage to be developed in the winding of this head or coil. Th output coils from the pick-up head II 2 are connected to transfer amplifier H3 which. causes the corresponding X signal to be recorded by the recording head I I4 in the cell passing under this recording coil at this time. The X signal recorded by the recording head III then continues around the drum and passes under the erasing head H8. Th erasing head comprises a permanent magnet or a continuously energized electromagnet oriented in such direction that the magnetization of the drum after passing under this head produces no output voltage in any of the pick-up coils under which this portion of th drum will pass. During the time the cell in which the X was recorded by the recording head III is 1'0- tating from the pick-up head H2 to the erasing head H8 and then on to the recording head I II again, the X recorded by the recording head H4 is also rotated around the drum so that at approximately the same time that the pick-up arm 25 again passes opposite segment 32b connected to line I4 in the manner described above, the X signal recorded in the cell assigned to line I4 on the drum in the channel associated with head H5 will pass under head II5. As a result the voltage induced in the pick-up head H5 and amplified by amplifier H6 causes a high positive voltage to be applied to the output X lead of amplifier H6 and causes a low positive voltage to be applied over the output lead from amplifier HS to the left hand terminal of diode 206 at this time, so that when this next high positive voltage applied to lead 42'! from the scanning mechanism due to the scanning of line I4 and the next corresponding high positive synchronizing pulse from the amplifier 60 are applied to diodes 208 and 204 and 205, the voltage of the X input lead to amplifier H0 is prevented from becoming positive, Consequently, no further signals will be recorded by the head III at this time so no further voltages will be induced in the pick-up head I I2 by the cell in the channel under head I I I assigned to line I4. However, the X signal recorded in the cell in the channel under heads H4 and H assigned to line I4 will remain until removed or changed in the manner described hereinafter.

The voltage from lead 427 is also applied to the left-hand input terminal of the gate G2 shown within rectangle 2H in Fig. 1. This gate is in turn connected through an amplifier I to a recording head I2I which amplifier and recording head are arranged to write or record only X signals upon the corresponding channel of the drum. Thus, each time the synchronizing pulse from the amplifier 60 is applied to the diode 2I4, a high positive pulse appears on the X lead from gate 2H when positive voltage is also applied to the diode 2I6 from lead 421. As pointed out above, such a high positive voltage is received from lead 421 and thus applied to the diode 2I6 each time the distributor or scanner arm passing adjacent the segments of a line over which line current is flowing with the result that an X signal is written in each of the cells in the channel under the recording head I2I assigned to-the respective lines having current fiowingover them. When these cells pass under the pick-up head I22, they induce voltages therein which are repeated by the repeating or transfer circuit I23 tothe recording head I24 which records corresponding X signals in the corresponding cells in this channel assigned to the respective lines.

Returning now to the X signal recorded in the cell assigned to line I4 in the channel under the head I22, as the drum rotates this cell passes from under the head I22 to the erasing head I28.

At this time this X signal is erased and the cell.

then continues to travel around the drum and again passes under the recording head I2I where an X signal is again written in this cell if current is still flowing in the line at this time. As pointed out above, the scanning arm 25 will again pass adjacent to segments 32a and 32b at this time.

Consider now the X signal written or recorded by the recording head I24. As the drum rotates, this X signal will pass under the reading or pick-up head I 25 and cause an output in the output amplifier I26 indicating that an X signal was recorded in the corresponding cell in a channel under the recording head I24. As this cell or area continues to rotate, it will pass under the erasing head I29 which changes the magnetization of this cell so that it is no longer capable of inducing any voltage in the pick-up head I25.

However, pointed out above, if current con tinues to flow in the line so that an X signal is again written or recorded by head I2 I, the corree sponding voltage will again be induced in the pick-up head I22 and transferred to the recording head I24 and recorded in the same cell assigned to line I4. The above operations then continue for each of the lines so long as line current flows over the lines. At this time it should be noted that the channel under the heads III and H2 does not have either an X signal or an 0 signal recorded in them; the previous recordings having been erased. The channel under the heads I2I and I22 has an X signal written or recorded in each of the cells each time these cells pass under recording head I2I so long as the corresponding line has current flowing in it. The X signals written in this channel arecontinually transferred to the recording head I24. X signals recorded by the recording head I24 in turn induce output voltages in the pick-up head I25 and then are erased by the erasing head I29 associated with the channel of heads I24 and I25.

The above-described operation of the various heads, coils, circuits, amplifiers, gates and scanning mechanism has been described with reference to line I4. The circuits respond in a similar manner to current flowing over line i5 and to all the other lines connected to the respective segments of the electrostatic scanning mechanism. As pointed out above, the voltage condition across the corresponding resistances of the respective lines causes X signals to be written in the cells of the respective channels described above assigned to the respective calling lines. The con dition of each of the calling lines is thus recorded in a predetermined cell or unit area on the surface of the magnetic drum assigned to the respective lines.

So long as the line It remains closed the potimes except the first one as described above,

high positive voltages exist at the X output leads and low voltages exist at the 0 output leads from amplifiers I I5 and I26 due to the X signals recordedin the cells or elemental areas of the drum assigned tov line I4, for. example, as these areas 21 or cells pass under the pick-up coils I I5 and I25.

In response to an opening of the line by the contacts of the dial I2 or contacts It! or otherwise the potential drop across resistors It and I8 falls to zero with the result that the voltage of lead 32? again becomes more negative as the rotating element 25 again passes segments 32c and 32b. As a result an X signal will not be recorded by either of the recording coils I2I or I i I and thus an X signal will not be recorded by the recording coil I24. As a result the next time the cell under coil I24 assigned to line It passes under the pick-up coil I25 positive voltage appears on the output lead instead. of on the X lead of amplifier I26. At the same time the X signal initially recorded by the recording coil I M will pass under the pick-up coil I I5 and cause a high positive voltage pulse transmitted over the X lead from amplifier IIE.

The outputs of amplifiers H6, I26 and I36 are connected to a translating or combining circuit I The combining circuit 25I comprises a plurality of two-element diodes which may be of a high vacuum type but as indicated in the drawing, these elements may also comprise crystal rectifiers of any suitable type including germanium and other types of rectifying contacts, semiconductors and the like.

As indicated on the left of the rectangle 255 an X0 lead extends from this rectangle which lead has a rectifier or diode connected between it and the X output lead from amplifier I iii. The XO- lead al o has a rectifier connected between it and the 0 lead from amplifier I255. ihese rectifiers are poled in such a direction that the voltage on the X0 lead is at a low value so long as the voltage on the X lead from amplifier II6 or the 0 lead from amplifier 525 is at a low value. If either of these outputs is negative the corresponding rectifier will conduct appreciable current from the battery 252 and thus maintain a voltage of the X0 lead at a relatively low value near the lowest value voltage applied to either X lead from amplifier H6 or the 0 lead from amplifier I26 whichever of these two leads is the lowest in voltage.

However, when an X passes under the pick-up coil H5 and a 0 passes under the pick-up coil I25 substantially simultaneously therewith, positive voltage appears on the X lead output from amplifier H 5 and on the 0- lead output from amplifier I26. As a result a high positive voltage is also applied to the X0 lead at this time.

Due to the previous magnetization of the other portions of the drum the output from the amplifier I 36 will be a high positive voltage on the 0 lead and a low positive voltage on the X lead at this time and until an X is recorded in the corresponding cells passing under these above-identified leads from the amplifiers II,

I28, I36 is a low positive voltage. However, as described above, the first time after line I4 has been opened and the slot assigned to this line passes under the pick-up coils II5, I25 and I35, a V

The XOO high positive voltage appears on the output leads from amplifiers H6, I26 and I36 connected to lead X00 through the diodes as describedabove. Consequently the voltage on lead X00 becomes high at this time. At the same time another cell or elemental area of the surface of the drum or cylinder assigned to line I4 passes under the recording coil I3I. The high positive voltage on lead X00 which is connected to the diode 222 in the gate circuit 22I causes a high positive voltage to be repeated on the X output lead of gate circuit 22! in response to a high positive synchronizing voltage pulse from amplifier 6c and the diode of gate circuit 22I. This X output lead extends to the recording amplifier I30 and the high positive voltage on this X lead in turn causes the recording coil I3I to record an X signal in the elemental area under this recording coil assigned to line I4. After a delay interval this X signal is transferred to the recording coil I34 and recorded in an elemental area under this coil at this time which elemental area is likewise assigned to line I4. When the X recorded by the recording coil I 34 passes under the pickup coil I35, it will cause the output on the 0 lead from amplifier I35 to be low and the voltage applied to the output X lead from amplifier I36 to become high. As a result positive voltage does not again appear on the X00 lead because the output voltage of the 0 lead from amplifier I36 is now low and thus maintains the voltage low on the X00 lead.

After the X signal recorded by the recording coil I3l passes under the pick-up coil I32 and is transferred to the recording coil I 34 as described above, it is erased by the erasing magnet or coil I38. Thus when the X signal passes under the pick-up coil I35 as described above, no high positive voltage ,appears on the X lead to the recording amplifier I39 and an X signal is not recorded in the elemental area assigned to line I4 at this time. recorded in the elemental area assigned to line I4 associated with the. pick-up coil. I35 until changed as will be described hereinafter.

So long as line I4 remains open no further signals are recorded by any of the recording coils III, I2I, H4 or IM with the result that high positive voltage appears on lead X0 each time the arms passes segments 32a and 32b and thus each time the X originally recorded by the coil H4 passes under the pick-up coil H5 in the manner described above. These high positive voltages are transmitted to a counting or timing circuit 270 and employed to indicate a disconnect or termination of the call in a manner to be described hereinafter.

However, assume that before any disconnect or termination signal is recognized due to the op eration of the counting or timing circuit 2H line I4 is reclosed. As a result the voltage on conductor or lead 42? becomes more positive when the distributor arm 25 next passes segments 32a and 3%. As a result an X signal will be recorded by the recording coil I2I in the delay section of the magnetic drum. A short interval of time later an X signal will be recorded by the recording coil I24 in the cell or elemental area thereunder assigned to line I 4 in a manner described hereinbefcre. When this portion of the drum passes under pick-up coil I25 the X signal originally recorded by the recording coil H4 also passes under the pick-up coil H5 with the result that high positive. volt-.

The X signal remains age appears on the Xoutput leads: from amplizfiers H6 and I25 and a low voltage is obtained from the output leads from theseamplifiers.

The )QIX lead from the translating or combini-ng circuit I has a diode connected between it and the X output leads from each of the amplifiers IIB, I26 and I30-with the result that a highrpositive voltage is obtained from this lead the first time the X originally recorded by the recording coil H4 and the X recorded by the coil I24 and the X recorded by recording coil I34 pass under the pick-up heads I15, I25 and I35 after the line I4 has reclosed.

Lead XXX extends to the diode 223 of the gate or translating circuit 22I and also to the diode 232 of the gate circuit 23 I. The high positive pulse applied to the diode 223 at this time causes an. 0 signal to be recorded in the cell or elemental area of the drum assigned to line I4 under the coil I3I at this time. Likewise, a high positive voltage on lead XXX at this time ap plied to the diode 232 causes an X signal to be recorded by the recording coil I4I which X signal is later transferred to the recording coil I 44 and recorded in another cell or elemental area of the drum under coil I44 which is likewise assigned to line I4.

The 0 signal recorded in the cell under coil I3I later passes under the pick-up coil I32 and is transferred to the recording coil I34. At the time this 0 signal is applied to the recording coil I34 the X signal previously recorded in the cell which is now under this coil and assigned to line I4, will be written over or changed to an 0 signal and thus in effect canceled and an 0 signal substituted therefore. Thus after the elemental areas assigned to line I4, pass under the coils II4, I24, I34 and I44 there will be X, X, 0 and X signals respectively stored or recorded in them.

Thus in response to the closure of a calling line such as I 4, an X signal is recorded by coils III and H4 in the cells or elemental areas assigned to said line I 4. These areas are in the channel designated GI. In response to the subsequent opening of the calling line I4 an X signal is recorded by coils I3I and I34 in the areas assigned to line I4. These areas are in the channel designated H herein. In response to the subsequent reclosing of the calling line I4 an X signal is recorded in the elemental areas or cells under coils MI and I44 assigned to line I4-. These areas are in the channel on the magnetic drum designated channel J herein.

Any of the above signals or sequences of signals, i. e., the closure of a calling line, the closure of the calling line followed by the opening thereof, or the closure of the calling line followed by an opening of that line which opening is followed by a reclosure of the line, may comprise a calling signal and the exemplary embodiment described in detail herein may be arranged to recognize and respond to any or all of the above calling signals. As shown in Fig. 1 the input lead I48 to the register and display apparatus is connected to the X output lead from amplifier I46 of channel J. Consequently, this equipment responds to the last type of call signals enumerated above. However, by connecting a lead similar to I48 to the X output lead from the amplifiers of other channels, such as GI or H, instead of from channel J the system will respond to the other call signals described above. When desired additional register and display equipment may be provided and connected to diflerent ones of r different digits, 1. e., a one or a zero.

the channels forrespondingto different types of.

call signals.

In order to display the call it is necessary that the display or registering mechanism be idle and properly reset to a zero condition. This registering equipment as shown in Fig. 1 comprises a plurality of counter tubes IOI I, IOI2, etc., reset multivibrator tube I050, a group of registering tubes I040, I04I, etc., indicating tubes I010, I0'II, etc., and reset tubes I060, IOBI, etc. A control and combining circuit comprising the diodes I53, I54, I and I50together with a repeating cathode follower tube 0I I is provided for controlling the registering equipment. The restoring multivibrator tube I050 is arranged so that the conduction within the sections of this tube automatically returns to the normal conditions after a restoring or reset operation. The circuit of multivibrator tube I050 is arranged so that with key I05I unoperated, as shown in the drawing, the left-hand section will be conducting and the right-hand section non-conducting due to the connection of the grid of the left-hand section to a more positive bias voltage than that applied to the grid of the right-hand section. Under these circumstances the voltage of the anode of the left-hand section is at a relatively low value so that the right-hand sections of gates I3I, I32, etc. are blocked at this time. The voltage of the anode of the right-hand section of tube I050 is at its most positive value when the right-hand section is conducting substantially no current. As a result, the positive voltage is applied to the upper terminal of diode I54, which voltage is in such a direction that it produces substantially no current flow through the diode because it is in a reverse direction to the mode of easy conduction of the diode.

The counter tubes I0 and IOI2 comprise two representative stages of a multistage binary counter employed to designate the line over which the calling signal or signals originate. In the binary number system each place or denominational order of a number has either one of two The tubes IOI I, IOI2, etc., represent each stage or denominational order and conduction of current by one section of such a tube represents a zero for that stage or denominational order and the other section conducting represents a one for that denominational order. Dhese counter stages are arranged to be reset once per revolution of the drum I04 as will be described hereinafter. Thereafter they count each of the synchronizing pulses which define the unit areas individual to the respective lines. In the exemplary embodiment of the present invention a synchronizing pulse is generated for and defines each of the elemental areas under the pick-up coils assigned to the individual calling lines and these elemental areas assigned a line are under the various pick-up coils as described above when the arm 25 passes the segments connected to that line. Consequently, thecondition of the counter tubes IN I, IOI2, etc., accurately identifies the line having elemental areas under the various pick-up coils at each instant of time.

As shown in the drawing the counter tubes IN I and IOI2 have been arranged so that they are reset to their zero or initial condition once per revolution by a negative pulse applied to them as will be described hereinafter. When these tubes are in their initial or zero condition, it is assumed that the right-hand triode is conducting current between its anode and cathode but that no current flows in the anode path of the left-hand section of these tubes.

The synchronizing or timing pulses after passing through the delay line 291 and the repeating and inverting tube 296 are applied to both sections of tube It! I through the coupling condenser H and the two diode rectifiers as shown in the drawing. The timing pulses as received from amplifier 60 through the delay line 2%?! are of a positive polarity. These delayed pulses are repeated by tube 2% as negative pulses and applied to the two coupling diodes. The diodes are poled in such a direction as to ofier a low resistance or impedance to negative pulses. Under the assumed conditions with the right-hand section of tube I OH conducting current, its anode will be at a lower voltage than the anode of the lefthand section. Consequently, the diode connected to this right-hand section will offer appreciably more impedance to the pulse than will the diode connected to the left-hand section. Furthermore, the application 01? a negative pulse through this right-hand diode to the anode of the righthand section of tube It! i and then through the coupling network to the control grid of the lefthand section produces no appreciable effect upon either section of this tube. However, the application of the negative pulse to the left-hand anode of tube H] II and then through the coupling condenser to the control grid of the right-hand section of this tube tends to reduce the current flowing in the right-hand section. As a result the voltage of the anode of the right-hand section tends to rise or become more positive and applies a more positive voltage to the control. grid of the left-hand section of tube Hill which tube then starts to conduct current and as a result its anode voltage falls tending to make the grid of the right-hand section still more negative. Consequently, the current previously flowing through the right-hand section of tube Nil l is interrupted and current flow through the left-hand section initiated.

Under these circumstances tube Hill indicates a count of one and remains in the above-described conducting conditions wherein current flows through the left-hand section but not through the right-hand section until the next timing pulse is applied to both sections of this tube.

The second delayed timing negative pulse is again applied to both anodes of tube lili in the same manner as above described. At this time, however, current flowing through the left-hand section is interrupted due to a negative pulse transmitted from the anode of the right-hand section oi tube It! I and the coupling network. to the control grid of the left-hand section. As a result of the consequent decrease in current flowing through the left-hand section, positive voltage is applied to the control grid of the righthand section which causes current to start to flow through this section.

Thus, upon the application of each of the olelayed negative timing pulses the conducting conditions in tube lill l are reversed.

The initiation of a discharge through the righthand section of tube it! I causes the voltage of the anode of this section to fall from substantially the full anode battery supply voltage to a much lower voltage which in turn applies a negative pulse through the coupling condenser and the rectifiers or diodes connected to the two anodes of tube 1M2. Under the assumed conditions, prior to the application of this negative pulse,

the right-hand section of tube H2 is conduc ing current while the left-hand section is not. The application of the negative pulse to the two diodes does not at once effect the cut-oif of the right-hand section. However, the application of the negative pulse through the diode connected to the anode of the left-hand section and then through the coupling arrangement to the control grid of the right-hand section reduces or interrupts the current flowing to the right-hand section of this tube thus causing the anode of this section to rise in voltage and apply a positive voltage to the grid of the left-hand section which then starts to conduct current and applies a still more negative voltage to the grid of the righthand section. In this manner the application of a negative pulse through the coupling condenser and coupling diodes causes the current flowing through the right-hand section to be interrupted and a flow of current through the left-hand section initiated.

Had the left-hand section been conducting cur rent instead of the right-hand, then the application of the negative pulse would be transmitted through the opposite diode and cause the interruption of the current flowing through the lefthand section and an initiation of current flowing through the right-hand section. In other words, upon the application of each negative pulse from the anode of the right-hand section of tube Hi! i, the discharge current within the tube ltifi is transferred from the previously conducting section to the other section. In a similar manner, each time the anode of the right-hand section becomes more negative due to the initiation of a flow of current to this section of tube ltl2, a negative pulse is relayed to the next counter stage and so on.

With the right-hand section of tube iiii i con ducting and the left-hand section of tube 1M2 conducting, these two tubes indicate a count of 2, since two synchronizing pulses have been applied to tube IDH as described above.

It should be noted that the counter tubes are advanced by delayed timing pulses. In other words, these counter tubes are not advanced until the undelayed timing pulses have controlled the gate circuits 538, I32, etc., in a manner described hereinafter. Consequently, the timing pulses control the gate circuits and accurately indicate the setting of the counter tubes in a manner described hereinafter before the counter tubes are advanced by the respective delayed timing pulses.

In a similar manner additional synchronizing pulses are counted by tubes till i, it i 2 similar tubes not shown in the drawing but provided when necessary. Thus the setting of con ducting conditions of the counter tubes of Hill, MHZ, etc., at all times accurately represents the identity of the calling line being tested or scanned at each instant of time.

Tubes H348 and i841 are gas-filled tubes having a gas pressure of a fraction of an atmosphere and in which the control grid loses control of the current flowing in the anode-cathode circuits once this current starts to flow. These tubes are initially set or conditioned with no current nowing in their anode-cathode circuits and are restored to this condition after each call has recorded and noted as will be described herein-- after. With each of the tubes iiiit. i l ii, etc. non-conducting their anodes are at a relatively high positive potential. However, the diodes ltd, i555, etc., are connected to the respective anodes of tubes I645 and WM in the direction to oppose the flow of current through these diodes when these tubes are non-conducting. However, this time the common terminal of the combi circuit which is connected to the grid of tube 51% I is maintained at a relatively low voltage by the output of amplifier I46 until an X signal recorded in channel J is picked up by the cor esponding pick-up coil I45.

Upon the sampling of line i l during the next revolution of the drum (a: after the X signal is recorded in channel J of the delay section of the drum the output of the X lead of ampl'fier I46 Will have a high positive voltage applied to its X lead due to the X signal recorded in this channel of the magnetic drum.

Under the assumed conditions the high positive voltage on the X lead I46! from amplifier is the last high positive voltage to be applied. to the diodes I53, I54, I55 and It?) with the result that the voltage of the common conductor of this combining circuit changes to a high positive value and tube ilII repeats a high positive voltage in its output or cathode circuit to diodes of the gate circuits 13L 1'32, etc. If the corresponding counter tube indicates a 1, the righthand sections will be non-conducting and have their anodes at a relatively high v. If, on the other hand, these counter tubes in. cate a count of zero the right hano' be conducting and its anode at a cor gondi low voltage with the result that the leitsections of gates I3I and I32 are Sl. blocked or ineffective to transmit a posi age to their common or output terminal.

Thus, during the time the X signal recs in channel J passes under the piclr-up and causes a high positive voltage to be to the output load I43 from amplifier l5 nosi tive voltage will be applied to all of terminals on the leit-hand side of the cuits 'I3I, I32, etc., when the synchronizing p" occurring at this time is received from the up coil 5:; and amplifier fill. As a result, the t I040, IMI, etc., which are individual to the counter tubes Iili I, Iii-l2, etc., which a count or digit value of 1 have a positive vol The tubes Hill,

or zero condition. As a result, the register tu I040, IMI, etc., have discharges initiated throu h them in accordance with the count the bi counter tubes IBII, IOI2, etc. In a. 1011, c high positive pulse from amplifier causes the counter to advance by a count of one. Thus '5 count of the binary counter designates or idol tifies the calling line which is assumed to be the line designated M in the drawing.

Generally the count of the binary counter which identifies the respective calling lines will not be the directory number of the calling line but may be such number or represent such num her when desired.

Indicating devices IE1!) and ItlI are connected in the cathode circuits of tubes Itdil and :GM and have discharges initiated through them at substantially the same time discharges are ini tiated in the corresponding register tubes I848 and IMI, thus indicating to an attendant the identity of the calling line. It is to be understood of course that relays, switches or other indicators or other types of mechanisms may be employed in addition to or in place of the gas tube indicators I010, IIIII, etc., for indicating the identity of the calling line or for responding to the call from the calling line in any desired manner. These responsive devices may actuate other switching devices, signals, buzzers, lamps and the like.

In addition, the initiation of a discharge through the register tubes I040, IBM, etc., causes the anode of the tubes through which discharge is initiated to fall to a relatively low voltage with the result that the voltage applied to the diodes I55, I55, etc., also fails to a relatively low value. Consequently, the voltage applied to the grid of tube BII also falls to this low value so that the output of tube 9 is no longer sufficient to permit positive voltages to be transmitted through the gate circuits -I3I, I32, etc., andas a result the register circuits will remain in the condition indicating the identity of a calling line until restored by an attendant or by other means.

When it is desired to restore the register circuits described above to their initial .or'zero condition, key I05I will be operated which applies a more negative voltage to'the grid of the lef-t-hand section of tube H359 for 1ashort interval of time during the charging time of the small condenser I952. As a result ofthe cross couplings of the monostable circuits of tube I059 the currentfiowing through this section is interrupted and current flow through the right-hand section of this tube initiated. As a result, the voltage applied to the diode I54 is reduced so that-further signals or high positive pulses received over conductor i l-8 cannot be relayed to the grid of tube 9H, even if and when the other input controls described herein would other dse permitpulscs :to be repeated from conductor I48 to the grid of tube 9H. In addition, the voltage of the lefthand anode of tube I050 becomes more positive and is applied through the right-hand terminals of gates 13I, I32, etc. As a result, positive voltage is applied to the grids of the restoring tubes I060, IIIGI, etc., during the application of synchronizing pulses to the gate circuits l'3I, I32, etc.

The application of positive voltages to the control elements of tubes I060 and HIE-I causes these tubes to conduct current with the result that the voltage of their anodes and the anodes of the register tubes I040, IMI, etc., is reduced. to a low value. The voltage of the cathodes of the register tubes is maintained for a short interval of time at the voltage resulting from the discharge current flowing through cathode resistor by the condenser connected around that resistor. The reduction of the anode voltage of these tubes 1M0, IE H, etc., is sufficient to reduce the voltage between the anodes and cathodes of these tubes, below the sustaining voltage required by the register tubes to maintain a discharge through them. As a result, the discharge'thrcugh these register tubes is interrupted and the register circuit restored to normal. Likewise, the indicating tubes I019 and IIlII are also restored to normal, thus canceling the identity of the previous called line.

Thereafter, as condenser IUBZ con-tinues to charge the voltage of the grid of the left-hand section of "tube I I approachesthe' voltagool the grid of the right-hand section. When these two grid voltages differ by less than the magnitude of the negative pulses as applied to the oathodes of both sections of tubes H355 the next delayed negative synchronizing or timing pulse applied to the cathodes of this tube causes the gridto-cathode voltage of the left-hand section to become sufficiently positive to initiate a flow of current through the left-hand section of tube WEE which in turn, due to the cross-connections between the sections of this tube, causes the current flowing through the right-hand section to be interrupted. As a result the voltage of the anode of the left-hand section falls to a relatively low value so that no further pulses are transmitted through the right-hand terminals of the ate circuits 73!, 132, etc. In addition, the voltage of the right-hand section of tube I056 rises so that positive voltage is applied to the diode I54 thus indicating that the register circuit is again in condition for responding to other X signals recorded in channel J.

The X signals recorded in the various channels as described above may be canceled or removed by applying signals to the corresponding recording amplifiers in response to the opening of key ID of line :4, for example, with the result that after a predetermined time of positive signals or pulses on the X0 lead at times assigned to line M for example, or after a predetermined number of said signals have been received over this lead, the timing circuit 279 functions and causes zeros to be written in all of the channels GE and J which may have X signals stored in them in the individual areas assigned to the respective calling lines.

It is thus evident that the calling arrangement described is capable of recording a call originating on any one or more of a plurality of lines and then register and indicate this fact and the identity of the line over which the calling signals originated. That portion of the equipment required to indicate these signals may later be restored to normal whereupon it is ready to register and indicate the signals received over the next line the elemental areas of which-have a complete series of signals recorded in them and which next pass under the pole tips of the pick-up coils. The identity of this line is also indicated. It is also evident that calls from all of the lines may all be substantially simultaneously recorded by the magnetic recording equipment and the associated electrostatic scanning or distributor mechanism.

When desired, the anode of the left-hand section of tube was or the output of the repeating tube 9! i may be connected to the right-hand side of gate circuit 23| and cause an 0 signal to be recorded in channel J in the elemental area of this channel assigned to line id, for example, with the result that after the indication of a call has actuated the register circuit and equipment the X signal in his elemental area of channel will be canceled and changed to an 0 signal.

Details of the recording amplifiers, recording coils, pick-up coils, pick-up amplifiers and transfer amplifiers and equipment are shown in Fig. 2. Here the two sections of the drum are illustrated as two drums wherein the delay drum or section of the drum is illustrated by drum Hi l and the storage section by drum M95. The recording amplifiers, such as He, are illustrated by tubes 3!! and 3H2; These tubes may be separate tubes as shown in the drawing or they may be sections of a twin tube. The tube 35! is employed to write or record X signals in the elemental areas of the corresponding channel, while tube 312 is employed to write or record 0 signals. Thus, each time a positive pulse is applied to the No. 2 terminal and thus through the coupling condenser to the grid of tube 3H current flows in the output or anode-cathode circuit of this tube and through the X winding of the recording or writing coil ill, for example. Conversely, when a positive pulse is applied through the coupling condenser to the No. 3 terminal positive voltage is applied to the grid of tube 3 l2 with the result that current flows in the output circuit of tube M2 and through the O winding of the recording coil i i i, causing an i) signal to be recorded in the elemental areas passing under this coil at this time.

The elemental areas recorded by the recording coil Ill then rotate part-way around the delay drum Hi5 and pass under the pick-up coil I I2, for example, and induce voltages in the two output windings of this coil. These voltages have the Wave forms illustrated by the small curves designated TX and T0 in response to an X signal or an 0 signal passing under the pick-up coil I I2. These voltages are applied through respective resistances to the grids of tubes 3H5 and 5H6. As shown in the drawings, tube 3| 5 has a condenser connected between its anode and grid which condenser in combination with said grid circuit resistance causes the combined circuit to operate as an integrating device and in effect integrates the signal applied to the control grid of this tube. Likewise, tube 3E6 has a condenser 3H3 similarly connected and integrates the voltage wave form applied to the control element or grid of tube 3H5 with the result that the output wave form of the anodes of these tubes is as illustrated by the curves designated fill-X and 311-0. It is to be understood that the tubes 3 i 5 and M6 represent a suitable amplifier which may comprise one or more stages of amplification, depending upon the extent of amplification required and the accuracy of the integration necessary. The output or" the integrating tubes 3! 5 and 3! 6 is connected to the control grids of tubes 32! and 322, respectively. These grids are also biased so that in the absence of a signal applied to them substantially no current flows in their output circuits. In addition, these grids are connected to a source of synchronizing signals received over lead 385 so that when positive synchronizing signals are applied to lead 385 and the voltage from either tube 3H5 or sill is at a high positive value, current will flow in the corresponding tube 32! or 322 and cause a corresponding X or 0 signal to be recorded in its elemental area. under the recording coil l M at this time.

Thereafter, the signal or signals are carried around the drum U and pass under the pole tips of the pick-up coil H5. The output of coil H5 is applied to the integrating tube 33! and associated circuit and integrated as before and then repeated by tube 332. The integrated signal applied to the grid of tube 332; comprises a voltage of relatively high amplitude in response to an X signal passing under the pole tips of coil H5 so a high positive voltage is repeated by the cathode of this tube to the X output lead. Conversely, when the integrated signal applied to the input of tube 332 comprises a voltage of relatively low amplitude in response to an 0 signal passing under the pole tips of coil M5, the anode of tube 33?. is at a high positive voltage in response to such 0 signals and this positive voltage is coupled through a gas or high vacuum diode 333 to the O output lead where it causes a high positive voltage to be applied to this lead. These voltages are employed in the circuits as desc 'ibed herein to control the various other recording and indicating circuits. The change in voltage applied to the lead in response to an X signal passing under pole tips and the change in voltage applied to the X lead in response to an 0 signal passing under the pole tips of the pick-up coils are both of low magnitude.

After the signal recorded by the recording coil iii as described above passes under the pick-up or reading coil l 82 it will pass under the erasing coil H3 be erased in the manner described hereinoeiore whereupon the elemental area assigned to the respective lines is again in condition to respond to signals recorded by the recording coil I I I.

It should be noted that the pick-up coils as shown in l. have their pole-pieces oriented with respect to the cylinder such that the air-gap extends Circu uferentially around the cylinder. Consequently, the recording coils orient the mag-- netic vectors circumferentially around the cylinder in their respective channels. As shown in Fig. 2 the air-gap is shown extending along the axis of the drum and at right angles to the arrangement shown in 1. The coil. IE8 has likewise seen shown rotated 90 degrees from that shown in Fig. 1. It is to be understood that the recording and pick-up coils as well as the other equipment operate with the coils in either orientation. However, in an exemplary embodiment the coils have been actually oriented as shown in l. The air-gaps of the coils have been rotated through substantially 90 degrees in the showing of Fig. 2 to aid in the drawing and understanding of the manner in which the various coils are located one relative to another and the flow of signals or pulses from the first recording coil through the delay drum and then to the storage drum. and finally to the final pick-up coil from the storage drum. It is to be understood, of course, that when desired the coils may be arranged as actually shown in 2, as satisfactory operation will be obtained when the coils are so arranged.

Al hough a specific embodiment of the invention has been shown in the drawing and describ in d t l herein, it will be understood that various modifications may be made without departing from the scope and spirit thereof as de fined in the appended claims.

What is claimed is:

1. In combination, an electrostatic scanning device comprising a plurality of stationary conductors arranged in pairs, shielding member interposed. between each of said pairs of station ary conductors. plurality of signaling circuits each comprisingtwo conductors, means including interconnections for connecting each of said conductors of each of said circuits to the individual stationary conductors of one of said pairs of stationary cond v tors for conveying voltages representing the s, aling conditions of said signaling circuits to said pairs of stationary conductors, a movable conductor, means for rotating said movable conductor past each of said stationary conrs in succession, and electrical means op- -ly interconnected with said movable conductor responsive to the combined voltage condioi the conductors of said circuits at the times said. movable conductor passes said pairs of stationary conductors.

2. In combination, a plurality of signaling lines each comprising two conductors, means for applying a voltage difference between said two conductors, an electrostatic scanning device comprising a fixed segment for each conductor of each of said signaling lines arranged in pairs, means for conveying voltages representing different signaling conditions from the conductors of said lines to the individual segments of a corresponding pair of said segments, a movable conductive element, means for moving said movable conductive element past said segments in sequence for obtaining a voltage condition on said movable element under control of the voltage impressed upon said segments at the time said movable elcment moves past said segments and electrical means operatively interconnected with said movable element for adding together the successive voltage conditions obtained from adjacent segments of each pair of segments.

3. In combination, a plurality of signaling lines each comprising two conductors, means for applying a voltage difference between said two conductors, an electrostatic scanning device comprising a fixed segment for each conductor of each of said signaling lines arranged in pairs, electrical interconnecting 163,115 for operatively interconnecting said conductors of each of said lines with individual segments of a corresponding pair of said segments, a movable conductive element. means for moving said movable conductive element past said segments in sequence for obtaining a voltage condition on said movable conductor under control of the voltage impressed upon said segments at the time said movable element moves past said segments, summing apparatus intercom nected with said movable element for adding together the voltage conditions obtained from adjacent segments of each pair of segments, and means electrically connected to said summing apparatus for restoring said summing apparatus during the time said movable element moves from the last segment of one of said pairs of segments to the first segment of a succeeding pair of segments.

4. In combination, a plurality of signaling lines each comprising a plurality of conductors, apparatus for applying a voltage condition to each of the conductors of said lines, a scanning apparatus for periodically sampling the voltage condition of each of the conductors of said lines, and storing means electrically and operatively connected to said scanning apparatus for storing an electrical quantity representing the voltage condition of one of the conductors of one of said lines, and apparatus also electrically and operatively connected to said scanning apparatus for adding to said stored quantity another electrical quantity representing the voltage condition of said other conductor.

5. In combination, a plurality of signaling lines each comprising a plurality of conductors, apparatus for applying a voltage condition to each of the conductors of said lines, a scanning device for periodically sampling the voltage condition of each of the conductors of said lines, storing means connected to said scanning device, said storing means including a condenser for storing a charge representing the condition of one of the conductors of one of said lines, voltage means connected to said scanning device for deriving a voltage representing the voltage condition of the other of said conductors and apparatus jointly responsive to said charge on said condenser and to said derived voltage, restoring apparatus con- 33 nected to said storage means to restore the charge on said condenser to a reference condition, and means for operating said restoring means in synchronism with said scanning device.

6. In combination in a scanning arrangement, a plurality of signaling lines for transmitting different signaling conditions, each of said lines having at least two line conductors, a plurality of segments, means for conveying voltages representing diife'rent signaling conditions from each of said line conductors of a line to adjacent ones of said segments, means for moving a scanning conductor adjacent to each of said segments in succession, electrical means operatively interconnected withsaid scanning conductor for combining the output from said adjacent segments to indicate the combined electrical conditionof said line conductors.

7. In combination, a plurality of signaling lines each having at least two line conductors, signal receiving apparatus comprising a scanning mechanism, a pair of electrodes included in said scanning mechanism for each of said lines, means for electrically and operatively interconnecting each of the line conductors with one of said electrodes individual to said line, apparatus for applying voltages of opposite polarities to said line conductors, a pick-up member, means for rotating said pick-up member past each of said electrodes, apparatus responsive to the voltage of said pickup member as it moves past said electrodes and instrumentalities for combining voltages of opposite polarity interconnected with said pick-up member for indicating the combined electrical condition of said line conductors each time said pick-up member moves past adjacent electrodes interconnected with said line.

8. In combination, a plurality of signaling lines each having at least two line conductors, signal receiving apparatus comprising a scanning mechanism, a pair of segments included in said scanning mechanism individual to each of said lines, means for electrically interconnecting each of the line conductors with one of the segments individual to said line, apparatus for applying voltages of opposite polarities to said line conductors, a pick-up member, means for rotating said pickup member past each of said segments, a condenser and a unilateral conductive device interconnected in series with said pick-up member for storing a voltage of one polarity obtained from said pick-up member as said pick-up member rotates past one of said segments, combining apparatus connected to said pick-up member for combining voltages of opposite polarity obtained from said pick-up member with said stored vol age, and amplitude responsive means connected to and controlled by said combining apparatus. 9. In combination, a plurality of signaling lines each having at least twd'line conductors,sigiial receiving apparatus comprising a scanning mechanism, a pair of electrodes included in said scanning mechanism individual to each of said lines, means for interconnecting each of the line conductors with one of the electrodes individual to said line, apparatus for applying voltages of opposite polarities to said line conductors, a pickup member, means for rotating said pick-up member past each of said electrodes, a condenser and a unilateral conductive device interconnected in series with said pick-up member for storing a voltage of one polarityobtained from said pickup member as said'pick-up member rotates past one of said electrodes and combining apparatus connected to said pick-up member for combining voltages of opposite polarity obtained from said pick-up member with said stored voltage as said pick-up member rotates past said electrodes.

10.- In combination, a plurality of signaling lines each having at least two line conductors, signal receiving apparatus comprising a scanning mechanism, a pair of segments included in said scanning mechanism individual to each of said lines, means for interconnecting each of the line conductors with one of the segments individual to said line, apparatus for applying voltages of opposite polarities to said line conductors, a pickup member, means for rotating said pick-up member past each of said segments, a condenser and a unilateral conductive device interconnected in series with said pick-up member for storing a voltage of one polarity obtained from said pickup member as said pick-up member rotates past one of said segments, apparatus for combining voltages of opposite polarity obtained from said pick-up member with said stored voltage, mag: netic storing mechanism for storing signals, and an amplitude responsive means responsive to combined outputs which exceed a predetermined value interconnected between said storage means and said pick-up means.

11. In combination in a scanning arrangement, a plurality of signaling lines each having at least two line conductors, a scannable element individual to each of said line conductors, means including interconnections between said scannable element and its respective line conductor for applying signalling conditions to the scannable elements under control of said lines, a scanning element, means for moving said scanning element adjacent each of said scannable elements in succession for inducing voltages on said scanning element, apparatus interconnected with said scanning element for combining the voltages induced on said scanning element as it passes adjacent scannable elements individual to a given line to indicate the combined electrical condition of said line conductors.

12. In combination, a scanning arrangement in accordance with claim 11 characterized in that said apparatus interconnected with said scanning element includes apparatus for summing the magnitude of the electrical condition of said scanning element as it passes adjacent the scannable elements interconnected with one of said lines.

13. In combination, a scanning arrangement in accordance with claim 11 characterized in that said apparatus interconnected with said scanning element comprises apparatus for summing the magnitude of the electrical condition of said scanning element as it passes adjacent the scannable elements interconnected with one of said lines, an output circuit and apparatus for applying one electrical condition to said output circuit when said scanning element passes adjacent the scannable elements connected to a closed line and apparatus for applying a different electrical condition to said output circuit when said scanning element passes said scannable elements connected to an open line.

14. In combination, a scanning arrangement in accordance with claim 11 characterized in that said apparatus interconnected with said scanning conductor includes means responsive to the rateofchange of the electrical condition of said scanning element, means for rendering said apparatus responsive to said rate-of change of the electrical condition of said scanning conductor effective when said scanningv conductor scans amass? 35 the scannable elements individual to one oi said lines.

15. In combination, a scanningarrangement in accordance with claim 11 characterized in that said apparatus interconnected with said scanning conductor includes means responsive to the rate of change of the electrical condition of said scan ning element, means for rendering said apparatus responsive to the rate of change of the electrical condition of said scanning conductor efl'ective when said scanning conductor scans the scannable elements individual to one 01 said lines, an output circuit, means for applying one'electrical condition to said output circuit in response' to the rate of change of the electrical condition of said scanning element as said scanning element passes adjacent the scannable" elements connected to one of said lines.

16. In combination; a scanning arrangement in accordance with claim I characterized in that the electrical means interconnected: with said movable conductor includes means responsive to a rate of change or voltage of said movable conductor and" apparatus for rendering said means effective as saidvmovable conductor scans the conductors of one of: said pairs of stationary conductors.

1'1. In combination, a scanning arrangement in accordance with claim 6 wherein said electrical means interconnected with said scan"- ning' conductor includes means for adding the magnitudeiof the'voltage induced on said scanning conductoras saidscanning conductor passes adjacent one of the segments connected to a line to the magnitude of the. voltage induced in said scanning. conductor" as said: scanning; conductor passes adjacent the segment connected to the other line conductor of said. line,

18. In combination, a scanning arrangement in accordance with claim 6 wherein. said electrical means interconnected with said con"- ductor includes differentiating: apparatus respon sive to the rate of change of voltage: 011 said scanning conductor as said scanning conductor moves between segments connected: tothe" line conductors of a given line.

19. In combination, a scanning arrangement in accordance with claim 6' wherein said electrical means interconnected with said scanning conductor includes differentiating apparatus respon sive to the rate of change of voltage of said scanning conductor as'said scanniirig conductormoves between segments connected to the line-conductors of a given line, switching apparatus for maintaining said differentiating apparatus not effective except when said scanning conductor passes between se mentsinterconnected with the line conductors of a line;

20; In combination; an electrostatic: scanning device comprising aplurality of stationary scannable conductors: arranged inv pairs; a shielding member interposed between each ofsaid pairs of stationary scannable conductors, a plurality of signaling circuits each comprising at least two conductors, means for applying a voltage condition to each of the conductors of said pair of stationary scannable conductors representingthe signaling condition of respective ones of the conductors of each of said. signaling circuits, a movable electrical scanning pickup device; means for rotating said movable pickup device in spaced relationship past each of. said: stationary scannable conductorsiin succession and, forming the condensers with. said: soannable conductors in succession, voltageresponsive means and. means for: applying voltages to said voltage responsive means under' control of the voltage induced on said movable scanning pickup device as'it moves past each pair'oi said fixed conductorsand means to. combine the voltage condition applied to said voltage responsive device in response to said movable pickup device moving pasta pair of said fixed conductors.

21. In" combination, a plurality of signaling lines for conveying different signaling conditions comprising at least two conductors for each 0! said lines, means for applying a different voltage condition to each of the conductors under control of the signaling conditions of each oi said lines, an' electrostatic seaming device comprising a fixed segmentfor each conductor of each of: said signaling lines arranged in pairs, means for applying voltage conditions" to said fixed conductors under control of the signaling conditions of each conductor of the respective lines, a movable: pickup element, means for moving said movable pickup" element past said segments insequence for obtaining a voltage condition by said movableelement under control 01 the voltage impressed uponsaid segments at the time said movable element moves past said segments and electrical means responsiveto the voltages applied to said fixed. conductors as said movable picliup element moves past said respective fixed conductors for adding, together the voltage conditions obtained from; adjacent segments of each pair of conductors.

22. In combination, a plurality ofsignaling lines each comprising a plurality of conductors, apparatus for applying an electrical condition toeach of the conductors of said lines, means controlled by signaling conditions received over the respective conductors of each of said lines for changing the electrical conditions of said condoctors, scanning apparatus for periodically sampling the electrical condition of each of said conductors of said lines and storingmeans for storing an electrical quantity representing the electrical conditionv of the first of said lines under control of receivedv signaling conditions, and means for adding to said stored quantity another electrical quantity representing the electrical condition of said other conductor.

23. In combination, a scanning mechanism including a plurality of signaling lines for trans mitting difierent signaling conditions: each of said lines having atleast two line conductors, a plurality of soannable segments, means for applying an: electrical condition to each of a plurality of said-segments under control of the signaling condition of the conductors of each of said lines, a movable scanning element, means for moving said scanning element adjacent to each of said scannablee segments in succession and inducin a voltage uponsaid scanning element, electrical means for combiningthe voltage. induced in said scanning element each time said scanning element moves pasteach pair of said segments, and means toindicate the combined electrical condition of said line conductors.

24. In combination, in a scanningsystem; a plurality. of signaling lines each having at least two line conductors for conveying a plurality of signaling conditions, ascannable element individual to each of said line conductors, means for applying different voltages to saidscannable element under control of different signaling conditlonsv of the respective: ones of said: signaling lines, a scanning element, for moving said scanning elementediacent each. said scamiabie 

